Karst features and optimization of karst foundation treatment in Luodi-Xinhua Expressway

Karst is developed in Luodi-Xinhua Expressway. Earth-caves and karst collapses are formed with groundwater table rapidly falling led by mining and pumping in the surrounding coal mine. In order to make the construction of expressway economically and securely, the karst subgrade is necessary to be treated. Firstly, through study and analysis on the factors affecting the foundation treatment, a foundation treatment scheme with multiple attribute and fuzzy property is optimized by means of multi-objective decision making fuzzy set theory and analytical hierarchy process. Secondly, based on the engineering geological conditions and the reinforcement effect as well as engineering cost, three schemes of karst foundation treatment are compared, including static pressure grouting, tube sinking compacted gravel piles and dynamic compaction with reinforced concrete continuous plate. The results show that the dynamic compaction with reinforced concrete continuous plate is the most optimal scheme which is of the highest degree of membership to excellence (up to 0.86), the lowest cost (only 13.5 million yuan) and good reinforcement effect. The cost, 13.5 million yuan, is respectively 1.7 and 3.6 million yuan less than the tube sinking compacted gravel piles and the static pressure grouting schemes.